I wonder how many people are going to learn probabilities all wrong because of this. Whatever they learn just won't feel right because hey all these games work the way it makes sense intuitively.
Imagine a coin that flips heads exactly every 2nd time because it's a 50% probability. Would make magnificent future casino patrons or startup employees or ... well a lot of things that rely on chance and probability.
I'm not sure if Dota2 has mitigations against that, but I've certainly seen it in other games.
Go and hit a neutral unit so that you have 2+ hits in a row without your ability/item proc'ing and then save the next hit for an enemy player since your next hit is likely to have a higher chance of proc'ing.
I think that's been patched now but it was there for a good while.
edit: My example's not averaging, forget which game I was using where they multiplied them together somehow.
You can see the code in there : https://twitter.com/m1sp/status/697268847187890176
It is increasing your chance to hit if you've a missing streak and if you have lost soldiers. And lower the chance of the enemy hitting you if they've already hit you this turn and you have less than 5 soldiers. So you can (and will) miss 90% shots, it should not happen twice in a row the same turn.
http://www.ufopaedia.org/index.php?title=Chance_to_Hit_(EU20...
I'm briefly recalling some lectures during University that we're hardwired to find patterns, even when there aren't any, and we make some pretty wild conclusions about the patterns we find this way. I've seen otherwise fairly reasonable players during DnD tell me it's time to "switch to the late night dice" because the current D20 hits a bad luck streak after awhile, and they adamantly adhere to this.
With games it's the same way. League of Legends tweaked it's crit chance algorithm to be a little less random because it could be so wildly swingy and players didn't like it - crit reliant champions would either feel amazing as they melted, or they'd feel useless after a series of successive non-crit attacks. The Dodge mechanic was removed almost entirely since a few select champs could have amazing fights where they got lucky and got 3+ dodges in a row even at relatively low dodge percentages.
It sucks to be the type of person that does understand probability in a reasonable way, but the evidence in games shows that just isn't how the grand majority of players operate.
Fire Emblem (another strategy game series) solves this problem by taking the average of two random numbers. If the average is lower than the "to miss" value, an action succeeds [0]. This skews the probabilities at the low and high ends so that an 80% chance becomes 92%, 90% becomes 98%, etc, to minimize the occurrence of "spearman defeats tank" scenarios where players assume a 1/10 chance of failure will never happen.
[0] http://serenesforest.net/general/true-hit/